I am withholding judgment on the grandparents for now. And I definitely don't think the grandparents had anything to do with Caylee's disappearance as some have suggested. On the 911 calls, Cindy is obviously reeling with stress at the realization that her granddaughter is missing.
From what I can gather from the media (and that's all we really have), as events unfolded I believe she went into severe denial. Cindy and George do not appear to be deceptive in a malicious way, but WANT so much to believe that Caylee is alive that they are in preservation mode. Who can blame them? I can't say I wouldn't react the same way. This is their child and grandchild. They WANT Caylee to be alive. They WANT to find her. They WANT to believe Casey. The mind is very powerful. As far as I can tell, their sole interest in is finding Caylee...they say it again and again and again.
More than likely, the reason Casey left is that Cindy and George became entirely fed up with their sociopath of a daughter...whether they enabled her to be this way or not is not something we can determine as some folks are just born that way (I don't have the studies or scientific documentation to post to back this up, but I am a scientist in the medical field with an interest in psychology...and scientist now recognize that babies are not born blank slates as once thought...NATURE is very powerful over NURTURE). We don't know much about Lee, but unless it comes out that Lee is some irresponsible dolt, I lean more towards Casey being an absolute disappointment to her parents who have continually struggled to help her become a productive person.
They kick her out or she moves out...a month later their granddaughter is discovered to be missing. They are freaking the heck out! In my opinion, their back conscience knows Casey is lying...but their mind will NOT allow them to hear that. If that baby is found and is deceased and Casey is proven to have done it...my bet is they do not support her anymore than minimally expected as they are and always will be her parents...and will probably feel immense guilt as such. However, I don't believe that Casey maliciously killed Caylee. If she is dead, it was an accident, but Casey was too afraid of disrupting her evening or weekend plans what with all the problems a dead child would cause...or maybe was doing drugs and was paranoid of being caught herself...and launched the cover-up scheme...which all fits the sociopathic personality without making her also a psychopath.
I, in no way, support anyone killing or even neglecting their child being protected from prosecution...but I do wish that every person out their can always count on the unconditional love of their parents. Cindy and George are showing their unconditional love. They aren't hampering the investigation. They have been completely cooperative as the police have stated multiple times. But they love their daughter. And there's nothing wrong with that...even when the daughter is as horrible as Casey. The fact that they are showing unconditional love tells me they were and are good parents. Give them a break. I feel awful for them.